Using requests to POST data

In the previous article we saw how to use the requests module to GET a web page from a webserver, essentially to pass data to a PHP script for processing. One drawback of this is that the data is unencrypted and visible to anyone who cared to look. If you wanted to send any sensitive information such as a username or password, using POST is much safer.

if ($_SERVER["REQUEST_METHOD"] == "POST") { $name = htmlspecialchars($_REQUEST['name']); $lastname = htmlspecialchars($_REQUEST['lastname']); echo "Welcome $name $lastname. You have made a POST request."; } else{ echo ' <form action="test2.php" method="POST"> <input type="text" value="First name:" disabled> <input type="text" name="name" ><br> <input type="text" value="Lastname:" disabled> <input type="text" name="lastname" ><br> <input type="submit" value="Submit"></form>'; }

The above PHP script, if requested from a browser (which uses a GET request), would show two text boxes for first and last name, and a submit button.
Completing the form, and clicking Submit, POSTs the information in the boxes to the PHP script, which then acts on the data.

The urequests module in Micropython can also sent POST requests, though it is not quite so straight forward as using GET. When I was experimenting on how to do this I drew a blank at first

It seemed simple at the outset. The general advice on multiple websites was to send the data in key pairs, either as data or as a json. Eg. Combinations such as:
data = {key1: value, key2: value2}
response = requests.post(request_url, data=data)

or use response = requests.post(request_url, json=data)
alternatively, use data_encoded = json.dump(data) and one of the above lines.

None of them worked, even if I tried different combinations, with either
headers = {'content-type': 'application/x-www-form-urlencoded'}
or headers = {'content-type': 'application/json'}

I finally found the answer though. The above will work in some form with Python, but MicroPython is a subset of Python, and to restrict it's size, hence the name, there are lots of Python that has not been included. Python Responses does a lot more behind the scenes encoding which uResponses does not.

In uPython, you have to encode the data as a string, and use the content header “headers = {'content-type': 'application/x-www-form-urlencoded'}”
For the string, just precede the key names with “&” and use an equals sign for the values.
data = {key1: value, key2: value2} becomes data = ‘&key1=value&key2=value2’

Very much like a GET query string without the first value being preceded by a question mark.
Eg. GET url/script.php?key1=value&key2=value2

url = "http://mywebsite/test_post.php?" #must send parameters as string preceeded by ampersand data_encoded = '&name=John&lastname=Smith' #must also specify this content header response = requests.post(request_url, headers = {'content-type': 'application/x-www-form-urlencoded'}, data = data_encoded) print(response.text)

So, if you call the PHP script shown above from urequests with a post request using this code, the response.text should read "Welcome John Smith. You have made a POST request."